Not sure what you mean by weekend 4. There are only 2 weekends of Coachella in April. This is taken from the website:
Coachella 2013 Dates

The dates for the Coachella Valley Music & Arts Festival in 2013 will take place on April 12 through April 14 at the Empire Polo Club in Indio, California followed by the next weekend on April 19 through April 21 at the same location.